You don't need to go far in Wellington's Newtown suburb to tap into someone else's wireless internet, with up to 55 properties broadcasting without any protection.
NetSafe has been out "wardriving" in suburbs in Wellington, Dunedin, and Auckland, to see which place had the best wireless security.
Wardriving involves travelling around with a wireless device checking security.
North Dunedin was the most secure, followed by Wellington, then Auckland.
NetSafe executive director Martin Cocker said the risk of unsecured wireless internet went beyond people using up bandwidths to download.
"By leaving a router unsecured or poorly protected it allows hackers to access all the devices on the network.
"People should also bear in mind that if they connect their computer, smartphone or tablet to public wi-fi hotspots, they are potentially sharing their information with others on that network.
"Free wi-fi is not the place to bank online, buy things, or read sensitive emails."
In Newtown, it picked up 2643 wireless signals.
Of those, 55 were open, which in theory meant they were unprotected. However, NetSafe noted some may still need further authentication.
Ninety-six had "broken" encryption, 1792 had "OK" encryption, and 15 were unknown.
In Newtown, 685 - or 25.9 per cent of the 2643 - wireless connections had state-of-the-art security.
On top of having "WPA2" security, NetSafe recommends people use strong passwords, update everything, secure wireless networks, back up files, and think before clicking on anything.
- The Dominion Post